Black Bottom Cupcake Without The Cream-Cheese?

I saw this picture in a magazine (they did not have a recipe) of a mint chocolate cupcake where the green mint filling was baked into the cupcake. You could tell it wasn't piped in after because it looked like a black bottom cupcake only with a green mint cream instead of cream cheese. (Here's a picture of a black-bottom cupcake: http://abview.files.wordpress.com/2008/11/creamcheese_cupcakes.jpg)

I was wondering if there was a way to get this result without using cream cheese? I've tried a buttercream-like mixture but it melts too much. If I made a mint buttercream mixture but added eggs and flour would this work?

I don't want the cream cheese taste, just a mint one and I don't want to just pipe filling in after the cupcake is done. Is there a way to do this?